Effect of temperature on systemic infection and symptom expression induced by Soybean yellow mottle mosaic virus in leguminous hosts

Temperature is one of the key factors influencing the viral disease development in plants. In this study effect of temperature on SYMMV accumulation and systemic movement was studied in French bean, mungbean and soybean cultivars by keeping them at temperatures range 22-25 °C, 26-29 °C and 30-33 °C. The proliferation of the virus under these conditions was confirmed through symptomatology, DAC-ELISA, RT-PCR with coat protein specific primers and RT-qPCR. French bean plants displayed symptoms by 12dpi at low temperature (22-25 °C) and by 3dpi at medium temperatures (26-29 °C) with continuous increase in viral accumulation from 0 to 24dpi. At high temperatures (30-33 °C), French bean did not show symptoms up to 12dpi but the virus accumulated and moved systemically. However, there was a decline in viral copy number after 12dpi. Mungbean plants showed mottling, mosaic and puckering symptoms at 22-25 °C and 26-29 °C and necrotic symptoms at 30-33 °C. Irrespective of temperature there was an increase in viral accumulation in mungbean from 0 days to 24dpi. Soybean plants showed veinal mild mottling at low and medium temperatures where as no peculiar symptom expression observed at high temperatures. Soybean also showed the reduction of viral copy number from 12 days to 24dpi at low and medium temperatures and from 6 days to 24dpi at high temperatures. These results indicate that temperature played an important role in SYMMV accumulation, movement and symptom expression in these three leguminous plant species. This study also demonstrates that SYMMV can replicate and spread in mungbean plants irrespective of the temperature.